This invention relates to a bleaching of hair, and more particularly to the use of intense radiation of artificial light for the bleaching of hair.
It is known that the coloring of hair is dependent upon the melanin content of the hair and such coloration is directly proportional to the melanin content. To some degree melanin has been shown to act as a "black hole" (D. Slawinska and J. Slawinski, Electronically Excited Molecules in the Formation and Degradation of Melanins, Physiol. Chem. Phys., 14, 363-374, 1982). The intensity of the photon field inside melanin might be higher than the external one by many orders of magnitude. The energy of the excited state of melanin stemming from light absorption is then dissipated as heat in the process based upon a single common mechanism, the electron-photon interaction (J. McGinnes and P. Proctor, The Importance of the Fact that Melanin is Black, J. Theor. Biol., 39 677-678, 1973).
Bleaching of hair color is typically performed through chemical means utilizing ammoniacal solutions of H.sub.2 O.sub.2 to degrade the melanin pigment. Although chemical bleaching of hair is very effective, it suffers from the disadvantage of causing significant oxidative hair damage as well as requiring lengthy treatment time to obtain sufficient color changes.
It is a common observation that prolonged exposure of hair to sunlight results in hair bleaching. The extent of such color change is a function of the initial hair coloring and the lightening process is very slow. Even during summertime, it takes many days of exposure in order to obtain perceptible hair lightening.
While our understanding of this bleaching process is not complete there is substantial experimental evidence suggesting that the lightening effect results from an interplay of physical (light absorption) and chemical (H.sub.2 O.sub.2 generation) factors.
Clearly, a possibility of relying exculsively on the light energy to bleach the hair (pure photobleaching) cannot be discounted and, indeed, this aspect has been brought up in a recent publication ("Laser And Hair", Tech. News, Laser Focus, Vol. 19, No. 9, p. 26, September 1983). However no practical efforts in this direction have been reported and no appreciation of, nor an understanding of the requirements of hairphotobleaching has been achieved.